Dissolution Rate Constants Research Articles

Ultrasonic dissolution of solid Al in liquid Sn during soldering: Modeling and equation, trend prediction, accelerating effect

Soldering of ceramics/metals using an inactive commercial solder with the advantage of low cost has wide application prospects. The dissolution behavior of base metal could not be quantified, which has been a basic issue for the joining design. This work investigated the dissolution of the solid Al in liquid Sn with and without the ultrasound. The physical model for the dissolving process was established based on the experiments. The relationship equation of the average concentration of Al (Ca) and soldering time was derived by using the Nernst-Brunner principle. The key parameters of limiting solubility (C0L) and dissolution rate constant (K) were obtained through dissolving experiments of liquid Sn to solid Al. The calculation results show that the effect of soldering temperature, and thickness Sn layer on the Al concentration (Ca) and dissolution rate (dCa/dt) under ultrasound is weaker than that without ultrasound. Compared to the condition without ultrasound, the value K, the maximum value of Ca and dCa/dt was increased by 5.8 times, 4.5 times, and 52 times at 250 °C under the ultrasound action, respectively, and the activation energy of dissolution was reduced by 41 %. The mechanism of ultrasonically accelerating dissolution of the solid Al by the liquid Sn has been revealed by using the bubble dynamics principle. It will provide a guideline for the design of soldering ceramics/metals using an inactive commercial solder.

Dissolution Behaviors of Recycled Cement Paste and Lime in EAF Slag Under Static Conditions

AbstractRecycled cement paste (RCP) is a CaO-rich resource that is recycled from waste concrete and waste cement. For reducing environmental impact and promoting comprehensive resource utilization, RCP could partially replace lime as flux in electric arc furnace (EAF) steelmaking process. In this study, the dissolution behaviors of RCP and lime in EAF slag at 1400 °C and 1500 °C were investigated using static dissolution experiments. The measured dissolution rate constant of lime at 1400 °C and 1500 °C is 3.12×10−5 and 8.42×10−5 m/s, respectively, while that for RCP is 1.37×10−4 and 2.91×10−4 m/s, respectively. For the lime dissolution, a dense dicalcium silicate (C2S) product layer was generated at the dissolution interface, with the diffusion of Ca2+ in the C2S layer being the limiting step for the lime dissolution. However, for the RCP dissolution, no product layer was observed at the dissolution interface. Instead, a dissolution intermediate layer forms due to slag penetration. During the dissolution of RCP, Ca2+ and SiO44− diffuse from RCP layer to slag, while Fe2+ and AlO45− diffuse from slag to RCP layer accumulating in the dissolution intermediate layer. Furthermore, a dissolution model was developed based on current experimental results, which helps to predict dynamic dissolution process of lime and RCP in EAF slag. In general, the dissolution rate of RCP in EAF slag was much higher than that of lime, partially adding RCP as flux in EAF could accelerate the liquid slag formation in EAF steelmaking process.

Modeling the Toxicokinetics of Suspensions of Soluble Metallic Nanomaterials.

Proper risk assessment of the many new nanoforms (NFs) that are currently being developed and marketed is hindered by constraints in time and resources for testing their fate and (eco) toxicity profile. This problem has also been encountered in conventional chemical risk assessments, where the definition of related chemical groups can facilitate risk assessment for all class members. Whereas grouping and read-across methods are well established, such approaches are in the early stages of development for NFs. In this study, a modeling framework was developed for grouping NFs into distinct classes regarding the contribution of released ions to suspension-induced toxicity. The framework is based on combining dissolution rate constants of NFs with information about the toxicokinetics of the NFs and the dissolution products formed. The framework is exemplified for the specific case of suspension toxicity of metallic NFs (silver and copper). To this end, principles of mixture toxicity and dose-response modeling are integrated to derive threshold values for the key NF properties determining suspension toxicity: size, shape, and chemical composition. The threshold values thus derived offer a possible solution for the high-throughput screening of NFs according to their morphological and compositional properties in a regulatory context.

Potential of CO2 sequestration by olivine addition in offshore waters: A ship-based deck incubation experiment

Ocean alkalinity enhancement is considered as an effective atmospheric CO2 removal approach, but currently, little is known about the carbon sequestration potential of implementing olivine addition in offshore waters. We investigated the effect of olivine addition on the seawater carbonate system by carrying out a deck incubation experiment in the Northern Yellow Sea; the dissolution rate of olivine was calculated based on the increase in seawater alkalinity (TA), and the CO2 sequestration potential was evaluated. The results showed that the dissolution of olivine increased seawater TA and decreased partial pressure of CO2, resulting in oceanic CO2 uptake from the atmosphere through sea-air exchange; it also increased seawater pH and mitigated ocean acidification to a certain extent. The addition of 1 ‰ olivine had a more significant effect on the seawater carbonate system than 0.5 ‰ olivine addition. The average dissolution rate constant of olivine was 1.44 ± 0.15 μmol m−2 d−1. Assuming that olivine settles completely on the seabed due to gravity, the theoretically maximum amount of CO2 removed by applying 1 tonne of olivine per square meter area in the Northern Yellow Sea is only 2.0 × 10−4 t/m2. Therefore, when olivine addition is implemented in the offshore waters, it is necessary to consider reducing the olivine size, prolonging the settling time of olivine in the water column; and spreading olivine in well-mixed waters to prolong the residence time through repeated resuspension, thus increasing its potential in carbon sequestration.

Influence of Mechanical Loading on the Process of Tribochemical Action on Physicochemical and Biopharmaceutical Properties of Substances, Using Lacosamide as an Example: From Micronisation to Mechanical Activation.

Many physical and chemical properties of solids, such as strength, plasticity, dispersibility, solubility and dissolution are determined by defects in the crystal structure. The aim of this work is to study in situ dynamic, dispersion, chemical, biological and surface properties of lacosamide powder after a complete cycle of mechanical loading by laser scattering, electron microscopy, FR-IR and biopharmaceutical approaches. The SLS method demonstrated the spontaneous tendency toward surface-energy reduction due to aggregation during micronisation. DLS analysis showed conformational changes of colloidal particles as supramolecular complexes depending on the loading time on the solid. SEM analysis demonstrated the conglomeration of needle-like lacosamide particles after 60 min of milling time and the transition to a glassy state with isotropy of properties by the end of the tribochemistry cycle. The following dynamic properties of lacosamide were established: elastic and plastic deformation boundaries, region of inhomogeneous deformation and fracture point. The ratio of dissolution-rate constants in water of samples before and after a full cycle of loading was 2.4. The lacosamide sample, which underwent a full cycle of mechanical loading, showed improved kinetics of API release via analysis of dissolution profiles in 0.1 M HCl medium. The observed activation-energy values of the cell-death biosensor process in aqueous solutions of the lacosamide samples before and after the complete tribochemical cycle were 207 kJmol-1 and 145 kJmol-1, respectively. The equilibrium time of dissolution and activation of cell-biosensor death corresponding to 20 min of mechanical loading on a solid was determined. The current study may have important practical significance for the transformation and management of the properties of drug substances in solid form and in solutions and for increasing the strength of drug matrices by pre-strain hardening via structural rearrangements during mechanical loading.

Alkaline flux dissociation in blast furnace tuyere bird’s nest: Part 1: CaO dissolution kinetics and slag physicochemical evolution in the coal-coke-slag

In the pursuit of optimizing smelting efficiency and minimizing carbon emissions in blast furnace operations, the strategic introduction of the tuyere alkaline flux injection, particularly in managing the viscosity of the coal-coke-slag in the bird’s nest region, is investigated. This study focused on exploring the dynamics of CaO dissolution within the slag of the coal-coke-slag in the bird’s nest area of a 2200 m3 blast furnace in China, particularly under conditions of instability. Quantitative analysis revealed that at 1550 °C, the CaO maximal dissolution capacity reached 62.05 wt%, with an average rate constant of dissolution observed at 4.65 × 10−4 s−1. The dissolution mechanism was characterized by interfacial dissociation, mass transfer diffusion, and the attainment of a dynamic equilibrium, predominantly influenced by the Ca2+ concentration gradient within the slag. This process facilitates the depolymerization of the slag’s network structure, heavily influenced by the aluminum oxide tetrahedron, effectively reducing slag viscosity. Further, the study quantified the optimal CaO injection content through the tuyere, suggesting a range of 4.00–5.32 kg/tHM, contingent on the use of high-quality raw fuel and advanced high wind temperature technology. This work contributes valuable theoretical insights towards enhancing the efficiency and sustainability of smelting operations, applicable to both conventional and high pellet blast furnaces, marking a significant step forward in the development of low-carbon metallurgical processes.

In-Situ-Generated Fluoride-Assisted Rapid Dissolution of Uranium Oxides by Ionic Liquids.

A quantitative, rapid, endothermic dissolution of U3O8 in C4mim·PF6 (1-alkyl-3-methyl imidazolium hexafluorophosphate) has been achieved within 2 h at 65 °C by in situ generated fluoride ions by pre-equilibrating the ionic liquid with suitable concentrations of nitric acid. The efficiency of the dissolution followed the trend: UO3 > UO2 > U3O8. The fluoride generation was found to increase with the concentration of nitric acid being equilibrated, the water content of the ionic liquid, and also the time of equilibration. The rate of dissolution of U3O8 followed the trend: C4mim·PF6> C6mim·PF6 > C8mim·PF6. The maximum loading observed for the present case was 200 mg mL-1 which is considered to be quite high with an ionic liquid. The effects of different acid pre-equilibration (HClO4, HCl) on F- generation and subsequent dissolution characteristics have also been investigated. The in situ F- generation, as well as U3O8 dissolution, were found to predominantly follow a pseudo-second-order rate kinetics, while the rate constants for U3O8 dissolution were found to be higher than that of F- generation. The dissolved uranium was successfully electrodeposited on a Cu plate, as confirmed by EDXRF, while the formation of UO2 was revealed from the XRD pattern of the deposit.

Analytical Study of Interstitial Fluid Extractive Microneedle Arrays Using Differential Transform Method

The computational studies of a predictive mathematical model for the extraction of interstitial (ISF) for transdermal and non-invasive diagnosis using biodegradable and hollow microneedle patch is presented in this paper. Rapid Diagnostic Tests diagnosis, which is non-invasive, affordable, straightforward, and provides results promptly and reliably, has increased access to parasite-based analysis on a global scale. Microneedle arrays are a rapidly evolving and promising technology for transdermal interstitial fluid extraction, which is used for many clinical diagnostic procedures. Hence, a developed mathematical predictive model used to optimize the design of microneedle patch for transdermal ISF extraction and subsequent diagnosis using dissolvable microneedle arrays was applied in this study. The model's solutions were obtained using the Differential Transform Method. The numerical Runge-Kutta method of fourth order was used to validate it. An experimental test result was also used to further validate the analytical results in the absence of the extracted velocity parameter. And there was a good agreement among them. Influence of dissolution rate constant, microneedle height, diffusion coefficient, velocity of ISF, microneedle ISF drug load, and density of the microneedle; were investigated. Increase in diffusion coefficient and density led to an increase in concentration of ISF extracted over time, an increase in dissolution rate led to a decrease in concentration extracted, while decrease in drug load and height, led to increase in ISF concentration extracted. A negligible effect was observed by varying the velocity of ISF extracted. The approximate analytical approach utilized in the current work has given us a more precise strategy for creating a mathematical model that predicts how ISF will be extracted from skin for use in transdermal and non-invasive rapid diagnostic tests.

Kinetics of Na- and K- uranyl arsenate dissolution

We integrated aqueous chemistry analyses with geochemical modeling to determine the kinetics of the dissolution of Na and K uranyl arsenate solids (UAs(s)) at acidic pH. Improving our understanding of how UAs(s) dissolve is essential to predict transport of U and As, such as in acid mine drainage. At pH 2, Na0.48H0.52(UO2)(AsO4)(H2O)2.5(s) (NaUAs(s)) and K0.9H0.1(UO2)(AsO4)(H2O)2.5(s) (KUAs(s)) both dissolve with a rate constant of 3.2 × 10−7 mol m−2 s−1, which is faster than analogous uranyl phosphate solids. At pH 3, NaUAs(s) (6.3 × 10−8 mol m−2 s−1) and KUAs(s) (2.0 × 10−8 mol m−2 s−1) have smaller rate constants. Steady-state aqueous concentrations of U and As are similarly reached within the first several hours of reaction progress. This study provides dissolution rate constants for UAs(s), which may be integrated into reactive transport models for risk assessment and remediation of U and As contaminated waters.

Dissolution–precipitation kinetics during C[formula omitted]S hydration: A holographic interferometry study

Tricalcium silicate C3S has been widely employed in model systems to interpret the complex mechanisms of cement hydration. The present study aims at providing an accurate description of the dissolution rate of C3S by implementing a new approach based on holographic interferometry. We propose a protocol that allows the measurement of the pure dissolution rate constant of the C3S phase by experiments performed in supersaturated conditions with respect to C–S–H. In these experiments, a flat polycrystalline surface of C3S was monitored in a quiescent solution. The amount of calcium released within the holographic cell was measured and the aqueous solution composition was constrained to the C–S–H stoichiometry at the interface. An equilibrium approach was applied to assess interfacial pH, saturation indexes, and C–S–H precipitation at the experimental conditions. The rate law of the pure dissolution of C3S was assessed in conditions ranging from far to close-to-equilibrium.

Structure‐Induced Enhanced Dissolving Properties of Mg(OH)2 Prepared by Glycine‐Assisted MgO Hydration

AbstractMg(OH)2’s dissolving properties have a considerable influence on its application performance. This study aims to improve the dissolving properties of Mg(OH)2 by modifying its crystal structure. Mg(OH)2 crystals with a large diameter‐to‐height ratio (≈40) structure are synthesized via a glycine‐assisted MgO hydration method utilizing glycine's differing adsorption energy on the (001) and (110) surfaces of Mg(OH)2 (−306.2 and −277.4 kJ mol−1). Compared to the control sample, the results of the dissolution kinetics investigation indicate that glycine‐assisted hydration considerably improves the apparent reaction rate constant of dissolution from 0.0020–0.0071 to 0.0039–0.0120 min−1. The enhanced dissolving properties are mostly induced by the large and thin crystal grain structure, which disintegrates easily during the dissolution process, exposing more reactive sites. The findings reported in this study provide a new approach to improving the dissolving properties of Mg(OH)2 that can enable its enhanced use in various applications.

Derivation of first-order dissolution rates to estimate particle clearance and burden in the human respiratory tract

Inhalation is a portal-of-entry for aerosols via the respiratory tract where particulate burden accumulates depending on sites of particle deposition, normal clearance mechanisms, and particle solubility. The time available for dissolution of particles is determined by the balance between the rate of particle clearance from a region and their solubility in respiratory solvents. Dissolution is a function of particle surface area divided by particle volume or mass (i.e., dissolution is inversely proportional to the physical diameter of particles). As a conservative approach, investigators commonly assume the complete and instantaneous dissolution of metals from particles depositing in the alveolar region of the respiratory tract. We derived first-order dissolution rate constants to facilitate biokinetic modeling of particle clearance, dissolution, and absorption into the blood. We then modeled pulmonary burden and total dissolution of particles over time as a function of particle size, density, and solubility. We show that assuming poorly soluble particle forms will enter the blood as quickly as highly soluble forms causes an overestimation of concentrations of the compound of interest in blood and other extrapulmonary tissues while also underestimating its pulmonary burden. We conclude that, in addition to modeling dose rates for particle deposition into the lung, physiologically based pharmacokinetic modeling of pulmonary and extrapulmonary tissues concentrations of moderately and poorly soluble materials can be improved by including estimates of lung burden and particle dissolution over time.

Reactive transport modelling under supercritical conditions

The utilisation of supercritical geothermal fluids depends on the assessment of the long-term effects of fluid-rock interaction on flow and transport behaviour. Reactive transport simulations are used for these assessments quantitatively based on high-quality thermodynamic and chemical data, understanding of the thermochemical constraints, and capability for accurate, stable, and rapid simulations. This work explores the precipitation/dissolution behaviour of basalt in water under supercritical conditions (400 °C and 502 bar) based on a comprehensive laboratory study conducted by Passarella (2021).The mineral reactions in the experiment were found to be largely kinetically controlled based on the model results. The final model dissolution rate constants were generally within an order of magnitude of the values calculated using the Arrhenius Law at 400 °C, based on published k25 and Ea values, paired with the reactive surface area estimates following the work of White and Peterson (1990). This indicates that the reaction rates at the experimental supercritical conditions are consistent with those observed at subcritical conditions for each mineral. It is theorised that this is because the properties of supercritical water at high pressures are comparable to subcritical water, specifically in terms of viscosity and the dielectric constant. A similar review of the final model precipitation rate constants showed better agreement with neutral dissolution rates extended to precipitation than the estimates following Horiuti (1957) for the experimental conditions.Mineral alterations during the experiment depended primarily on glass dissolution based on the model. Fluid saturation relative to the other minerals increased from the release of glass dissolution products, affecting their dissolution rates. Glass dissolution was also the primary source of components for secondary mineral formation, including celadonite, which also depended on olivine dissolution to provide magnesium. Upon glass depletion, the dissolution rates of the remaining primary minerals increased, and celadonite dissolved. Chlorite was deposited later in the modelled experiment than the other secondary minerals.

Distribution and dissolution kinetics of biogenic silica in sediments of the northern South China Sea

The dissolution efficiency of sedssimentary biogenic silica (bSiO2) dramatically affects the regeneration of dissolved silicic acid (dSi) at the sediment-water interface, which is a crucial pathway to maintain Si balance and silicic productivity growth in marine environments. We conducted wet alkaline leach and flow-through experiments to explore the dissolution behaviors of sedimentary bSiO2 in the northern South China Sea (NSCS), one of the largest marginal sea continental shelves. The bSiO2 contents of surface sediments were 0.64 - 2.06%, with an average of 1.04 ± 0.35%, varying with isobath water depth. The solubility of bSiO2 in surface sediments ranged from 227 μmol L-1 to 519 μmol L-1, and the dissolution rate constants varied from 0.67 to 1.53 yr-1 under specific conditions in lab incubation. The correlation between the biogenic materials (bSiO2, OC, and TN) revealed a different preservation pattern of bSiO2 in finer (Φ > ~ 5.5) and coarser (Φ< ~ 5.5) sediments. The high concentration of Al in sea water and “Al – detrital – bSiO2” interactions in sediments significantly interfered with the apparent solubility and dissolution dynamics of bSiO2. We combined the regional characteristics (primary production, bottom current, and resuspension-deposition) and the reconstructed dissolution kinetics of bSiO2 explained the mismatch between the surface (diatom biomass)/(total phytoplankton biomass) ratio and the sedimentary bSiO2/OC ratio, and the mismatch between the surface bSiO2 primary productivity and the bSiO2 sediment records in the NSCS. The resuspension-deposition, the higher reconstructed rate constants (0.94 ± 0.13 yr-1), and the dissolution rate (0.20 ± 0.01 yr-1) were responsible for the lower bSiO2/OC ratio (0.45 ± 0.28) at the inner shelf, and the winnowing process at the outer shelf with the lower reconstructed reactivity (0.30 yr-1) and dissolution rate (0.001 yr-1) led to the good preservation of bSiO2 in the upper slope. Furthermore, through the comparison with other sea areas, the relatively lower reactivity (1.12 ± 0.3 yr-1) of bSiO2 in sediments supported the notion that the NSCS sediments may serve as an important silica sink in the world ocean silica cycle.

Optimization of the stability constants of the ternary system of diclofenac/famotidine/β-cyclodextrin by nonlinear least-squares method using theoretical equations

This study aimed to establish a new method for determining the stability constants of drug/β-cyclodextrin (β-CD) complexes when multiple drugs interacting with each other coexist in the solution of complexation. The basic drug famotidine (FAM) and the acidic drug diclofenac (DIC) were used as model drugs, their solubility decreasing owing to their mutual interaction. The dissolution of both FAM and DIC was characterized by AL-type phase solubility diagrams in the presence of the other’s 1:1 complex with β-CD. When the stability constant was calculated from the slope of the phase solubility diagram using the conventional phase solubility diagram method, it was modified in the presence of the other drug. However, by performing optimization calculations that considered the interactions between the drug/β-CD complex and the drug, drug/β-CD complexes, and drugs, we were able to accurately calculate the stability constant of DIC/β-CD and FAM/β-CD complexes even in the presence of FAM and DIC, respectively. The results of the solubility profile indicated that various molecular species, which are attributed to drug-drug and drug/β-CD interactions, interfere with the values of the dissolution rate constants and saturated concentration in the solubility profiles.

Measurements and modelling of FeCO3 solubility in water relevant to corrosion and CO2 mineralization

FeCO3 is present as a CO2 corrosion product in many industrial processes and takes part in the natural CO2 mineralization process. This work presents the solid-liquid equilibrium of the system FeCO3-H2O at 5-120 °C. The FeCO3 solubility showed little temperature dependence. However, temperature affected kinetics as the rate constants for FeCO3 dissolution increased with temperature. The activation energy of FeCO3 dissolution in water was determined to 1.55 kJ mol-1. Gibbs energy of formation was found to be -653.27 kJ mol-1 and the enthalpy of formation for FeCO3 was -710.01 kJ mol-1 using the Extended UNIQUAC model. Extended UNIQUAC could predict the experimental solubility data of FeCO3 in water within an average absolute relative deviation of 0.08. The data obtained in this study creates the basis of reducing the consequences of CO2 corrosion and increasing knowledge of the CO2 mineralization process.

Behavior and Kinetic Mechanism Analysis of Dissolution of Iron Ore Particles in HIsmelt Process Based on High-temperature Confocal Microscopy

In this study, high-temperature confocal microscopy (HTCM) was used to perform in situ observations of the dissolution of iron ore particles in slag at different temperatures. Moreover, the shrinking core model (SCM) is used to explain the kinetic mechanism of the dissolution of iron ore particles. The area of the undissolved fraction of iron ore particles was used to analyze the dissolution rate of iron ore particles. The results show that the kinetic mechanism of dissolution of iron ore particles can be well explained by the SCM. The dissolution of iron ore particles is controlled by the diffusion of iron ore fractions in the boundary layer. The dissolution temperature, the concentration difference of iron ore fraction at the two ends of the boundary layer, and the initial particle size of iron ore particles affect the dissolution rate of iron ore particles. The dissolution rate constant was fitted by introducing a dissolution mechanism. The activation energy of iron ore dissolved in the CaO–SiO2–MgO–Al2O3–FeO slag system is 679.13 kJ/mol. The equation for the dissolution rate constant of iron ore in HIsmelt slag is summarized.

Predicting the in vitro dissolution rate constant of mineral wool fibers from fiber composition

Objective We developed predictive formulae for the in vitro dissolution rate constant kdis of acid-soluble synthetic vitreous fibers (SVF), paralleling our earlier work with glass wools, which are typically more soluble at neutral pH. Developing simple models for predicting the kdis of a fiber can allow prediction of in vivo behavior, aid fiber developers, and potentially reduce in vivo testing. Methods The kdis of several acid-soluble SVF were determined using high simulant fluid flow/fiber surface area (F/A) conditions via a single-fiber measurement system. Four fluids were employed, varying in base composition and citrate levels. Equations predicting the kdis were derived from fiber chemistry and dissolution measurements for two of the fluids. Results Testing of several fibers showed a ∼10× increase in the kdis when citrate was included in the simulant solution. Data from tests with Stefaniak’s citrate-free Phagoloysosmal Simulant Fluid (PSF) yielded kdis values aligned with expectations from in vivo results, unlike results from citrate-containing modified Gamble’s solution. Predictive equations relating fiber chemistry to kdis showed reasonable agreement between the measured and predicted values. Conclusions Citrate inclusion in the solution under high F/A conditions significantly increased the measured kdis. This resulted in more biorelevant data being obtained using the PSF fluid with the high F/A method used. The developed predictive equations, sufficient for fiber development work, require refinement before a recommending their use in place of in vivo biopersistence testing. Significant fit improvements are possible through additional measurements under these experimental conditions.

Formulation of Nifedipine–Polyvinyl Pyrrolidone (PVP) Solid Dispersion System and Intrinsic Dissolution Rate Evaluation

Nifedipine is a drug that acts as an antihypertensive and anti-angina. Nifedipine is known as a drug with poor water solubility. This characteristic will affect the intrinsic dissolution rate so that it can affect the absorption process and reduce the amount of drug that reaches systemic circulation. One of the strategies to increase the intrinsic dissolution rate is developing nifedipine to solid dispersions form. This study aims to observe the intrinsic dissolution rate of nifedipine after it has been made into a solid dispersion. Four samples were prepared, including three solid dispersions of nifedipine-PVP K-30 and one sample of pure nifedipine. The results of the intrinsic dissolution tests are then interpreted through the intrinsic dissolution rate constant (G). The solid dispersions with concentration of nifedipine-PVP K-30 90%:10%; 75%:25%; 60%:40% (w/w), and pure nifedipine produced G values of 3.63; 9.33; 12.63; and 2.08 µg/mm2. min1, consecutively. It shows that the formulation of nifedipine-PVP K-30 solid dispersions has higher G values than pure nifedipine. In addition, increasing PVP K-30 concentration up to 40 % (w/w) can increase the intrinsic dissolution rate of the nifedipine-PVP K-30 solid dispersion system.

Effects of salinity and temperature on seawater dissolution rate of initial detonation agent mercury fulminate

Mercury fulminate (HgFu) was used as an initial detonator for World War I and II munitions. Its presence in previously discarded and dumped munitions could potentially supply mercury pollution into coastal ecosystems where bygone weaponries reside. There is evidence that historical munitions have already contributed mercury pollution in coastal environments, and millions remain embedded in sediments and subjected to further weakening via corrosion under environmental conditions. Experiments were undertaken assessing HgFu dissolution under varying temperature and salinity conditions to constrain controls on mercury release into marine environments. Our results show that HgFu discharge is strongly temperature dependent, with dissolution rate constants increasing from ∼0.4 mg cm−2 d−1 at 5 °C to ∼2.7 mg cm−2 d−1 at 30 °C. No significant differences were observed between freshwater and seawaters up to 36 psu, except at 5 °C. These experiments provide a basis for modeling HgFu release from underwater munitions and its dynamics in coastal environments.